WASHINGTON (CNN) -- Former White House spokesman Scott McClellan says top administration officials -- including President Bush and Vice President Dick Cheney -- were involved in his "unknowingly" passing along false information about the leak of a CIA operative's identity.

Then-White House spokesman Scott McClellan briefs reporters in 2006.

In October 2003, as controversy grew about the leak of Valerie Plame's name, McClellan stood at the White House podium and said that Karl Rove, the president's top political adviser, and I. Lewis "Scooter" Libby, Cheney's chief of staff, had not been involved.

"There was one problem. It was not true," McClellan writes in his new book, "What Happened," which is to be released in April.

The excerpt -- three paragraphs from a 400-page book -- reads in full:

"The most powerful leader in the world had called upon me to speak on his behalf and help restore credibility he lost amid the failure to find weapons of mass destruction in Iraq. So I stood at the White House briefing room podium in front of the glare of the klieg lights for the better part of two weeks and publicly exonerated two of the senior-most aides in the White House: Karl Rove and Scooter Libby.

"There was one problem. It was not true.

"I had unknowingly passed along false information. And five of the highest ranking officials in the administration were involved in my doing so: Rove, Libby, the vice president, the president's chief of staff, and the president himself."

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McClellan has not given any specifics about how he believes Bush, Cheney, Libby, Rove and then-Chief of Staff Andrew Card were involved in the dissemination of false information.

Asked about the released excerpt, White House spokesman Scott Stanzel said, "The president has not misled his spokespeople, nor would he."

McClellan, who was White House press secretary from July 2003 until April 2006, said he's still writing the book and that his publisher had highlighted the excerpt to build interest.

Peter Osnos, founder and editor at large of PublicAffairs Books, said Wednesday that the book won't say Bush deliberately lied.

"Scott's not suggested that the president was himself party to a conspiracy to mislead. But it's pretty damn clear that other people knew what they had done and didn't tell the truth," Osnos said.

Osnos said the excerpt was released at this time because the company's book catalog came out Tuesday and reporters had begun asking questions.

Card appeared frustrated Wednesday that McClellan was not releasing more information to clarify the issue.

"I would never, cannot imagine that I would have knowingly asked Scott McClellan to say something that's a falsehood," Card said.

Plame, who has filed a civil suit against Cheney, Libby and Rove over the leak, issued a statement saying she was "outraged to learn" that McClellan had confirmed "he was sent out to lie to the press corps and the American public."

"McClellan's revelations provide important support for our civil suit against those who violated our national security and maliciously destroyed my career," she said. (A federal judge threw the lawsuit out in July on jurisdictional grounds; Plame's husband, Joe Wilson, said they are in the process of appealing, and hope the suit will be heard early next year.)

Wilson, a former U.S. ambassador who accused the Bush administration of misrepresenting intelligence on Saddam Hussein's weapons of mass destruction in the run-up to the 2003 invasion of Iraq, called for a new congressional investigation.

"I think it would be helpful to have congressional hearings on this matter," Wilson said. "This is a betrayal of the national security of the country."

In March, Libby was convicted of perjury and obstruction of justice for lying to investigators and a federal grand jury about his contacts with reporters concerning Plame.

Just before Libby was to report to a federal prison in July to serve 30 months behind bars, Bush commuted his sentence, although the president stopped short of a full pardon and Libby still had to pay a $250,000 fine.

Rove, who left the White House staff at the end of August, was not charged in the case. His attorney has acknowledged he was one of two sources cited by syndicated columnist Bob Novak, who first disclosed in July 2003 that Plame worked for the CIA shortly after Wilson wrote a critical op-ed piece for The New York Times.

Former Deputy Secretary of State Richard Armitage has since acknowledged he was Novak's original source for the information that Plame worked at the CIA, although he said the disclosure was not deliberate and he did not know at the time she was a covert agent.

Because deliberately leaking a CIA operative's name can be a federal crime, a special prosecutor, Patrick Fitzgerald, was appointed to investigate the case.

No one was charged in connection with the leak itself; Libby's charges resulted from statements he made during the investigation.E-mail to a friend